1. Field of the Invention
This invention relates to conductive polymer materials, and to conductive polymer materials having organic ions, a dopant and solvated free electrons. This invention also relates to conductive polymer materials used in microelectronics, optoelectronics and biomedicine.
2. Description of Related Art
Electrical conductors play fundamental roles in many aspects of modern technology. Technological advances in computers relies upon conductors that have low resistance. The energy required to move electrical current through a conductor is related to the resistance. To maintain operating temperatures, resistive energy losses, including heat, must be dissipated by devices containing conductors. To minimize the energy required and the energy dissipation necessary, it is desirable to provide conductors having very high conductivity and low resistance. Because many applications occur at temperatures near room temperature, it is especially desirable to provide conductors that have very high conductivity at near room temperature.
Metals and metal alloys are widely used as electrical conductors in many applications, including semiconductor applications. Metal conductors are characterized by the presence of a crystal lattice having no chemical bonds between metal and other atoms. Metals and alloys have resistance low enough and conductance high enough (about 106 S/cm) to be useful for many applications. However, the resistance of these materials is sufficiently high as to require significant energy for their operation, and their use results in substantial power losses.
A major advance in conduction occurred with the discovery in 1911 by Onnes, that below a certain critical temperature, certain metals can become superconductors, that is, have resistance to direct current (DC) approaching zero. The low resistance is related to conductivities greater than about 106 S/cm. Unfortunately, the critical temperatures for most metals is very low, typically a few Kelvins (K). This low temperature requirement severely limits the application of metal superconductors for room temperature applications.
Another significant advance occurred in 1987 with the discovery that certain ceramic oxides can become superconductors below critical temperatures of about 100 K. Although the critical temperature is substantially higher for ceramic oxide superconductors than for metal conductors, the temperatures are so low as to make room temperature applications expensive and difficult.
U.S. Pat. No: 4,325,795 (incorporated herein fully by reference) discloses methods of manufacturing and materials composed of greater than 10% by weight powdered bismuth metal suspended in epoxy resin, a dielectric polymer. In this process, the bismuth and epoxy form small filaments having diameters in the range of about 10 Å to about 1000 Å. The conductivity of the filaments exceeds that of metals (i.e., 106 S/cm) at room temperatures.
Theoretical analyses by W. A. Little (Physical Reviews 134:A1416 (1964), incorporated herein fully by reference), provided a basis for the formation of superconducting polyconjugated polymers having quasi-one-dimensional structures. Little's theories has led to the discovery of certain highly conductive polymer systems, including polyacetylene. When doped, polyacetylene can exhibit conductivity near that of metals (i.e., about 105 S/cm). Another type of highly conductive polymer was discovered by Grigorov et al., (Polymer Science 35 :(11):1625-1633 (1993), incorporated herein fully by reference). These polymers include undoped oxidized atactic polypropylene and polydimethylsiloxane, which are reported to provide structures having conductances greater than 1011 S/cm.
U.S. Pat. No: 5,777,292 (incorporated herein fully by reference) discloses organic macromolecular matrices containing conducting threads having conductances above 106 S/cm.